Oh another important point that I forgot...Daito ryu, Yoshinkan and Abe Sensei all stress opening the fingers widely. Very important to each style of aiki / kokyu / ki...very important.

Best,
Ron

Thank you Ron for sharing your toughts about kokyu.

The wide opening of the fingers is also a feature of Iwama-style aikido. In fact many Iwama-style students would probably extend their arm/hand/fingers as an answer if you would ask them what kokyu is.
Also the closing of the armpits (elbows pointing down) has been stressed during my training.